The present invention relates to a printing press having a perfecting station. More specifically, the present invention relates to a printing press having a perfecting station wherein the perfecting station includes a multi-purpose drum for printing and transferring a printed substrate. The present invention also relates to a printing press having a printing unit which is easily accessible in order to perform necessary maintenance procedures.
Printing presses that are capable of printing an image on both sides of a sheet are well known in the art. One way in which two sided printing has been achieved was by running a sheet between two blanket cylinders which simultaneously print the front and reverse side of the sheet as it passes there between. It is also known to send a sheet through a printing press in which the first side of a sheet is printed and then reversing the sheet and sending it through to print on the reverse side of the sheet. Printing on the reverse or backside of a sheet is referred to as perfecting. Prior art two sided printing machines are shown in U.S. Pat. Nos. 4,471,695 and 4,621,576.
Linear type printing presses that print a sheet at various stations along a conveyer are also known. Such presses are able to perfect a sheet by adding a perfecting printing station to the line either before or after the front side printing stations. However, these types of linear presses consume a considerable amount of floor space and are not practical for small shops. Set up and maintenance of these presses is also fairly time consuming.
In order to minimize press size and conserve floor space, it has been known to print sheets attached to a central impression drum. Sheets traveling on the central impression drum travel past various printing stations where an image is imparted onto the sheets. U.S. Pat. No. 4,967,660 discloses a central impression drum type printing press that is capable of printing on both sides of a sheet. In the ""660 patent, the discharge cylinder both assists in transporting the sheet from the main impression cylinder to outside the press and acts as an impression cylinder for the perfecting of the sheet. The discharge cylinder works in cooperation with a sprocket and endless chain, the chain carrying a plurality of mechanical grippers. The grippers are carried by the chain rotate over the discharge cylinder and capture the sheet from the central impression cylinder. The grippers then carry the sheet over the discharge drum to a point where it passes between the discharge drum and blanket cylinder. After perfecting is completed, the printed sheet is carried by the chain driven grippers until it is deposited in a finished sheet collection point. While the surface of the discharge drum is used as an impression cylinder, a separate mechanism including the grippers, endless chain and sprocket, is required in order to transport and discharge the paper. In addition, in order to accommodate the chains and mechanical grippers, a notch must be formed in the discharge cylinder. Due to this complicated construction, maintenance of the perfecting unit could be rather involved. Removal of the discharge cylinder in order to clear a jam or clean the impression cylinder surface would require removal of the chains and/or sprocket resulting in a time consuming operation.
In addition, the sheet after being printed on the first side proceeds directly to the perfecting station without processing by a dryer or other type of ink fixing unit. Accordingly, the image on the first side must air dry sufficiently before it contacts the exit drum to prevent smearing of the image. Therefore, the speed at which sheets are printed is limited by the drying time of the ink.
Printing presses are also known for their need for frequent maintenance which may include removing sheets after a jam is detected. Maintenance includes cleaning the various blanket cylinders and other interior areas of the press in order to ensure a quality output. While performing servicing, it is important that the press be down for as short of time possible in order for the maximum efficiency of the press to be realized. In printing presses having a central impression drum and a plurality of individual printing units spaced thereabout, access to various parts of the press becomes an issue. Since this type of press is a rather compact unit it is often difficult to get to the various areas in which maintenance needs to be formed. For example, in printing presses in which a dryer is installed between two of the printing stations, the dryer must often be removed in order to gain access to the interior portions of the press for maintenance. Removal of the dryer can require unfastening a variety of fastening hardware and then physically lifting the dryer off of the unit and placing it somewhere where it will be safely stored. Once maintenance is completed, the unit must then be placed back into position and refastened to the machine. Such an operation of simply removing the dryer to gain access can be rather involved and take a significant amount of time.
Accordingly, it would be desirable to provide a printing press that is capable of printing on the front and reverse side of a substrate wherein the exit or discharge cylinder includes a sheet attachment mechanism formed thereon and the exit cylinder also functions as an impression cylinder for a perfecting printing unit. It would also be desirable to provide a printing press which is easily maintainable and provides quick and easy access to all areas such that scheduled and unscheduled maintenance may be quickly performed thereby reducing the downtime of the press.
It is an advantage of the present invention to provide a printing press having a perfecting station to permit printing on both sides of a substrate.
It is another advantage of the present invention to provide a printing press having an ink fixing device rotatably secured to the press to allow case of maintenance. The ink fixing device may be positioned between a first side printing station and the perfecting station in order to fix the ink on the first side of a substrate prior to perfecting.
It is a further advantage of the present invention to provide a printing press having a perfecting station including a multi-purpose drum which performs the functions of both an exit drum and an impression drum.
It is still a further advantage of the present invention to provide a printing press having a delivery table translatable between an extended and a retracted position to permit operator access to aid in servicing the press.
These and other advantages of the present invention may be obtained by providing a printing press including a frame and a central impression drum rotatably supported on the frame. A plurality of first side printing stations is circumferentially spaced about the central impression drum and in communication therewith. Each of the plurality of printing first side printing stations is adapted to print an image on a first side of a substrate. A perfecting printing station is disposed at a position about the central impression drum. The perfecting printing station includes a multi-purpose drum having a substrate retainer for securing the substrate thereto. The multi-purpose drum forms an impression cylinder and is in communication with an image transfer cylinder for imparting an image on a second side of the substrate. An ink fixing unit is disposed between the first side printing stations and the perfecting station. The ink fixing unit fixes the image on the first side of the substrate prior to the image being imparted on the second side of the substrate by the perfecting station.
The present invention may also provide a printing press including a printing unit. The printing unit including a frame and a central impression drum rotatably supported on the frame adapted to transport a sheet. A plurality of first side printing stations is circumferentially spaced about the central impression drum and in communication therewith. The first side printing stations are adapted to impart an image to a first side of the sheet being transported by the central impression drum. A perfecting printing station is disposed at a point about the central impression drum sequentially after the plurality of first side printing stations for imparting an image to a second side of the sheet. The perfecting printing station includes a multi-purpose drum having a first sheet retainer attached thereto for securing the sheet to the multi-purpose drum. The multi-purpose drum forming an impression cylinder and being in rolling communication with an image transfer cylinder for printing an image on the second side of the sheet.
The present invention may further provide a printing press including a frame and a central impression drum rotatably supported on the frame and adapted to transport a sheet. A plurality of first side printing stations are circumferentially spaced about the central impression drum and in communication therewith for printing an image on a first side of a substrate. An ink fixing device for fixing the image on the first side of the substrate is pivotally secured to the frame and rotatable between a first position and a second position.
The present invention may still further provide a printing press including a printing unit for imparting a printed image to a substrate. The printing unit includes an exit station from which a printed substrate exits the printing unit. A delivery table is positioned adjacent the exit station for receiving and transporting the printed substrate. The delivery table is translatable between an extended position wherein the delivery table is in operative communication with an exit station of the printing unit and a retracted position wherein when the delivery table is in the retracted position operator access between the printing unit and the output table is provided.
A preferred form of the printing press, as well as other embodiments, objects, features and advantages of this invention, will be apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.